A method for recycling expanded polystyrene

Abstract

A process for manufacturing an expanded polystyrene foam article from used expanded polystyrene foam articles in combination with virgin polystyrene foam, the process comprising the steps of: stacking a plurality of individual used expanded polystyrene foam articles in a vertical block machine to occupy at least 20% of the internal volume in the block machine; conveying virgin polystyrene beads into the internal volume of the vertical block machine to occupy at least some of the remaining internal volume of the block machine by mixing the virgin polystyrene with the used stacked foam articles; and heating the internal volume of the block machine to a temperature of at least 75° C. by supplying pressurised steam into the heated internal volume of the block machine to fuse the virgin expanded polystyrene beads and the stacked expanded polystyrene foam articles to form the expanded polystyrene foam article.

What is claimed: 
     
         1 . A process for manufacturing an expanded polystyrene foam article from used expanded polystyrene foam articles in combination with virgin polystyrene foam, the process comprising the steps of:
 stacking a plurality of individual used expanded polystyrene foam articles in the vertical block machine to occupy at least 20% of the internal volume in the block machine;   conveying virgin polystyrene beads into the internal volume of the vertical block machine to occupy at least some of the remaining internal volume of the block machine by mixing the virgin polystyrene with the used stacked foam articles;   heating the internal volume of the block machine to a temperature of at least 75° C. and   supplying pressurised steam into the heated internal volume of the block machine to fuse the virgin expanded polystyrene beads and the stacked expanded polystyrene foam articles to form the expanded polystyrene foam article.   
     
     
         2 . A process in accordance with  claim 1  wherein the-heating step is carried out by introducing heat into the internal volume of the block machine before stacking said plurality of used expanded polystyrene foam articles to raise the temperature of the internal volume to at least 75° C. and more preferably to a pre-heating temperature in the range of 80° C. to 90° C. 
     
     
         3 . A process in accordance with  claim 1  wherein the conveying step comprises conveying the virgin polystyrene beads in combination with a pressured gas into the internal volume of the vertical block machine. 
     
     
         4 . A process in accordance with  claim 3  wherein the virgin polystyrene beads in fed in combination with the pressured gas at a pressure of 0.5 Mpa for a pre-determined time period into the internal volume of the vertical block machine. 
     
     
         5 . A process in accordance with  claim 1  wherein the stacking step comprises positioning the individual used expanded polystyrene foam articles in a spaced relationship relative to the internal walls of the block machine defining the internal volume of the block machine. 
     
     
         6 . A process in accordance with  claim 1  wherein the stacking step involves positioning the expanded polystyrene foam articles upon feet members in order to position the expanded polystyrene foam articles in a spaced relationship relative to a base of the block machine and wherein the feet members comprises expanded polystyrene foam. 
     
     
         7 . A process in accordance with  claim 1  wherein the internal volume of the block machine is defined by a base with a plurality of side walls, a front wall, a back wall and a top wall and wherein the stacking step comprises positioning the stacked expanded polystyrene foam articles to be spaced away from any one or more of the side walls and top walls by at least 100 mm and more preferably at least 150 mm. 
     
     
         8 . A process in accordance with  claim 7  wherein the stacking step comprises positioning the stacked expanded polystyrene foam articles to be spaced away from any one or more of the side walls by at least 100 mm and more preferably at least 150 mm and to be spaced away from front and the rear wall by at least 30 mm. 
     
     
         9 . A process in accordance with  claim 1  wherein the stacking step comprises stacking the plurality of individual used expanded polystyrene foam articles in a vertical block machine to occupy 30% to 40% of the internal volume in the block machine. 
     
     
         10 . A process in accordance with  claim 1  wherein the internal volume of the block machine is heated to a temperature in the range of 75° C. to 90° C. 
     
     
         11 . A process in accordance with  claim 10  wherein the internal volume of the block machine is heated to a temperature in the range of 75° C. to 85° C. and more preferably in the range of 79° C. to 81° C. 
     
     
         12 . A process in accordance with any one of the preceding claims wherein the pressurised steam is supplied into the heated internal volume of the block machine at a pressure of at least 0.5 Mpa for a predetermined time period. 
     
     
         13 . A process in accordance with  claim 12  wherein the pressurised steam is supplied from a steam accumulator into the internal volume of the block machine in an initial pressurised steaming step at a pressure of at least 0.6 MPa for an initial time period in the range of 10s to 40s and more preferably 20s to 30s and still more preferably 24s. 
     
     
         14 . A process in accordance with  claim 12  wherein the pressurising step further comprises a subsequent pressurised steaming step in which steam is supplied at a pressure of at least 0.3 MPa for a subsequent time period of 5s to 20s and more preferably for a time period of 10s. 
     
     
         15 . A process in accordance with  claim 1  further comprising a cooling step whereby upon supplying steam into the internal volume, the internal volume of the block machine is cooled, preferably air cooled to a cooling temperature in the range of 70° C. to 90° C. and preferably 75° C. to 80° C. and more preferably in the range of 79° C. to 81° C. 
     
     
         16 . (canceled)